#pragma once
#include <cstdint>
#include <vector>
#include <cstring>
#include <stdexcept>

// =============== Windows ==============
#if defined(_WIN32) || defined(_WIN64)
#include <ws2tcpip.h>
#include <winsock2.h>
#pragma comment(lib, "ws2_32.lib")
#define close(sock) closesocket(sock)
using socket_t = SOCKET;
#define INVALID_SOCKET_VALUE INVALID_SOCKET
#else
#include <arpa/inet.h>
#include <sys/socket.h>
#include <unistd.h>
#define INVALID_SOCKET_VALUE -1
using socket_t = int;
#endif

// =============== CRC16查表算法 ==============

// CRC 高位字节值表
static const uint8_t auchCRCHi[] = {0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, //
                                    0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, //
                                    0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, //
                                    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, //
                                    0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, //
                                    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, //
                                    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, //
                                    0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, //
                                    0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, //
                                    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, //
                                    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, //
                                    0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, //
                                    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, //
                                    0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, //
                                    0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, //
                                    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40};

// CRC 低位字节值表
static const uint8_t auchCRCLo[] = {0x00, 0xC0, 0xC1, 0x01, 0xC3, 0x03, 0x02, 0xC2, 0xC6, 0x06, 0x07, 0xC7, 0x05, 0xC5, 0xC4, 0x04, //
                                    0xCC, 0x0C, 0x0D, 0xCD, 0x0F, 0xCF, 0xCE, 0x0E, 0x0A, 0xCA, 0xCB, 0x0B, 0xC9, 0x09, 0x08, 0xC8, //
                                    0xD8, 0x18, 0x19, 0xD9, 0x1B, 0xDB, 0xDA, 0x1A, 0x1E, 0xDE, 0xDF, 0x1F, 0xDD, 0x1D, 0x1C, 0xDC, //
                                    0x14, 0xD4, 0xD5, 0x15, 0xD7, 0x17, 0x16, 0xD6, 0xD2, 0x12, 0x13, 0xD3, 0x11, 0xD1, 0xD0, 0x10, //
                                    0xF0, 0x30, 0x31, 0xF1, 0x33, 0xF3, 0xF2, 0x32, 0x36, 0xF6, 0xF7, 0x37, 0xF5, 0x35, 0x34, 0xF4, //
                                    0x3C, 0xFC, 0xFD, 0x3D, 0xFF, 0x3F, 0x3E, 0xFE, 0xFA, 0x3A, 0x3B, 0xFB, 0x39, 0xF9, 0xF8, 0x38, //
                                    0x28, 0xE8, 0xE9, 0x29, 0xEB, 0x2B, 0x2A, 0xEA, 0xEE, 0x2E, 0x2F, 0xEF, 0x2D, 0xED, 0xEC, 0x2C, //
                                    0xE4, 0x24, 0x25, 0xE5, 0x27, 0xE7, 0xE6, 0x26, 0x22, 0xE2, 0xE3, 0x23, 0xE1, 0x21, 0x20, 0xE0, //
                                    0xA0, 0x60, 0x61, 0xA1, 0x63, 0xA3, 0xA2, 0x62, 0x66, 0xA6, 0xA7, 0x67, 0xA5, 0x65, 0x64, 0xA4, //
                                    0x6C, 0xAC, 0xAD, 0x6D, 0xAF, 0x6F, 0x6E, 0xAE, 0xAA, 0x6A, 0x6B, 0xAB, 0x69, 0xA9, 0xA8, 0x68, //
                                    0x78, 0xB8, 0xB9, 0x79, 0xBB, 0x7B, 0x7A, 0xBA, 0xBE, 0x7E, 0x7F, 0xBF, 0x7D, 0xBD, 0xBC, 0x7C, //
                                    0xB4, 0x74, 0x75, 0xB5, 0x77, 0xB7, 0xB6, 0x76, 0x72, 0xB2, 0xB3, 0x73, 0xB1, 0x71, 0x70, 0xB0, //
                                    0x50, 0x90, 0x91, 0x51, 0x93, 0x53, 0x52, 0x92, 0x96, 0x56, 0x57, 0x97, 0x55, 0x95, 0x94, 0x54, //
                                    0x9C, 0x5C, 0x5D, 0x9D, 0x5F, 0x9F, 0x9E, 0x5E, 0x5A, 0x9A, 0x9B, 0x5B, 0x99, 0x59, 0x58, 0x98, //
                                    0x88, 0x48, 0x49, 0x89, 0x4B, 0x8B, 0x8A, 0x4A, 0x4E, 0x8E, 0x8F, 0x4F, 0x8D, 0x4D, 0x4C, 0x8C, //
                                    0x44, 0x84, 0x85, 0x45, 0x87, 0x47, 0x46, 0x86, 0x82, 0x42, 0x43, 0x83, 0x41, 0x81, 0x80, 0x40};


inline uint16_t CRC16(const char *ptr, int len) {
	uint8_t uIndex, crcH = 0xFF, crcL = 0xFF;
	while (len--) {
		uIndex = crcH ^ *ptr++;
		crcH   = crcL ^ auchCRCHi[uIndex];
		crcL   = auchCRCLo[uIndex];
	}
	return (uint16_t(crcH) << 8) | crcL;
}

// =============== 命令类型定义 ==============
enum Command : uint8_t {
	SGW_SUMMON    = 0x00,
	SGW_SYNCHRO   = 0x01,
	SGW_HEARTBEAT = 0x02,
	API_PING      = 0x10,
	API_LOGIN     = 0x11,
};

// =============== Magic结构体实现 ==============
/**
 * Magic字段结构（无union/位域，跨平台安全）
 *  15    14  ... 8   7 ... 0
 * +-----+--------+----------+
 * |rout |  flag  |   cmd    |
 * +-----+--------+----------+
 * routed: bit15 (1位)
 * flag  : bit8~14 (7位)
 * cmd   : bit0~7  (8位)
 */
struct Magic {
	uint16_t value;

	static constexpr uint16_t ROUTED_MASK = 0x8000;
	static constexpr uint16_t FLAG_MASK   = 0x7F00;
	static constexpr uint16_t CMD_MASK    = 0x00FF;

	Magic() : value(0) {}
	Magic(bool routed, uint8_t flag, uint8_t cmd) {
		assert(flag <= 0x7F && "flag should be 7 bits");
		value = (static_cast<uint16_t>(routed ? 1 : 0) << 15) | (static_cast<uint16_t>(flag & 0x7F) << 8) | (static_cast<uint16_t>(cmd));
	}
	explicit Magic(uint16_t v) : value(v) {}

	bool routed() const { return (value & ROUTED_MASK) != 0; }
	uint8_t flag() const { return static_cast<uint8_t>((value & FLAG_MASK) >> 8); }
	uint8_t cmd() const { return static_cast<uint8_t>(value & CMD_MASK); }

	void set_routed(bool routed) { value = (value & ~ROUTED_MASK) | (static_cast<uint16_t>(routed ? 1 : 0) << 15); }
	void set_flag(uint8_t flag) { value = (value & ~FLAG_MASK) | ((flag & 0x7F) << 8); }
	void set_cmd(uint8_t cmd) { value = (value & ~CMD_MASK) | (cmd & 0xFF); }
};

// =============== 协议头结构体 ==============
#pragma pack(push, 1)
struct Header {
	Magic magic;
	uint16_t data_len;   // 载荷长度(payload)
	uint16_t frag_id;    // 分片ID
	uint16_t frag_count; // 分片总数
	Header() = default;
	Header(uint8_t cmd, uint8_t flag = 0, bool routed = false, uint16_t len = 0, uint16_t fragId = 1, uint16_t fragCount = 1) :
	    magic(routed, flag, cmd), data_len(htons(len)), frag_id(htons(fragId)), frag_count(htons(fragCount)) {}
};
#pragma pack(pop)

// =============== 路由信息结构体 ==============
#pragma pack(push, 1)
struct Address {
	uint32_t ip;   // 网络字节序
	uint16_t port; // 网络字节序
	Address() : ip(0), port(0) {}
	Address(uint32_t ip_, uint16_t port_) : ip(ip_), port(port_) {}
};
#pragma pack(pop)

// =============== UDP消息结构体（打包/解包） ==============
class Message {
public:
	Header header;
	std::vector<Address> routers; // 路由记录，只有routed==true时才有
	std::vector<uint8_t> payload; // 动态payload

	// 构造
	Message(uint8_t cmd, const std::vector<uint8_t> &pl, uint8_t flag = 0, bool routed = false) :
	    header(cmd, flag, routed, static_cast<uint16_t>(pl.size())), routers(routed ? 4 : 0), payload(pl) {}

	Message() = default;

	// 打包成二进制流
	std::vector<uint8_t> pack() const {
		std::vector<uint8_t> buf;
		// Header
		buf.insert(buf.end(), reinterpret_cast<const uint8_t *>(&header), reinterpret_cast<const uint8_t *>(&header) + sizeof(header));
		// Routers
		if (header.magic.routed()) {
			for (const auto &addr: routers)
				buf.insert(buf.end(), reinterpret_cast<const uint8_t *>(&addr), reinterpret_cast<const uint8_t *>(&addr) + sizeof(addr));
		}
		// Payload
		buf.insert(buf.end(), payload.begin(), payload.end());
		// CRC16
		uint16_t crc = CRC16(reinterpret_cast<const char *>(buf.data()), buf.size());
		buf.push_back(crc & 0xFF);
		buf.push_back((crc >> 8) & 0xFF);
		return buf;
	}

	// 解包（反序列化）二进制流
	// throw std::runtime_error on CRC error or too short
	static Message unpack(const uint8_t *data, size_t len) {
		if (len < sizeof(Header) + 2) throw std::runtime_error("too short for header+crc");
		const Header *hdr   = reinterpret_cast<const Header *>(data);
		size_t offset       = sizeof(Header);
		size_t routers_size = hdr->magic.routed() ? sizeof(Address) * 4 : 0;
		if (len < sizeof(Header) + routers_size + 2) throw std::runtime_error("too short for routers+crc");

		size_t payload_len = ntohs(hdr->data_len);
		if (len < sizeof(Header) + routers_size + payload_len + 2) throw std::runtime_error("too short for payload+crc");

		// CRC校验
		uint16_t crc_recv = data[sizeof(Header) + routers_size + payload_len] | (data[sizeof(Header) + routers_size + payload_len + 1] << 8);
		uint16_t crc_calc = CRC16(reinterpret_cast<const char *>(data), sizeof(Header) + routers_size + payload_len);
		if (crc_recv != crc_calc) throw std::runtime_error("crc error");

		// 反序列化
		Message msg;
		msg.header = *hdr;
		if (hdr->magic.routed()) {
			msg.routers.resize(4);
			memcpy(msg.routers.data(), data + offset, sizeof(Address) * 4);
			offset += sizeof(Address) * 4;
		}
		msg.payload.assign(data + offset, data + offset + payload_len);
		return msg;
	}
};
